A modern passenger aircraft commonly includes an airframe having one or more control surfaces that control the orientation of the airframe as it moves through the atmosphere. Examples of control surfaces include ailerons, elevators, and rudders, to name just a few. The control surfaces are rotatably mounted to the airframe and rotate in response to control inputs from the aircrew during flight operations.
Conventionally, control surfaces are mounted to the airframe via one or more hinges that both support the control surface on the airframe and that permit the control surface to pivot with respect to the airframe. In a conventional arrangement, a linear actuator is used to control rotation of the control surface. The linear actuator is mounted to the airframe at one end and to a bell crank arm at the opposite end. The bell crank arm is mounted to the control surface. The linear actuator actuates in response to an input (e.g., a pilot pulling back or pushing forward on the yoke). Upon actuation, a piston in the linear actuator extends or retracts (depending on the input) in a linear manner. This moves the bell crank arm which, in turn, causes the control surface to pivot about the hinge that connects it to the airframe.
While this arrangement is satisfactory for current designs, there are limits to its application. As aircraft are designed to fly increasingly higher and faster (e.g., supersonic), the use of thinner airframes and thinner control surfaces become necessary. The use of thinner airframes and thinner control surfaces reduces the amount of space available to house the conventional arrangement described above. As the volume available for housing this arrangement diminishes, the length of the bell crank arm must be correspondingly reduced. As the length of the bell crank arm is reduced, the amount of torque required to move the control surface will increase. This need for increased torque requires the use of a more powerful linear actuator. The use of a more powerful linear actuator requires more robust support structures and more robust hinges. The more robust that the support structure and the hinges are, the more volume they will consume. This increased consumption of volume leaves even less room for the bell crank arm which must now shrink even further, causing a new cycle to begin and yielding a spiral of self-defeating solutions.
Some solutions to this challenge have been employed, but none are particularly desirable. In one solution, bulges and protrusions have been designed into the airframe to provide added volume to accommodate the larger components. This solution is undesirable because it gives rise to unsightly deviations from an otherwise smooth outer mold line. Additionally, in the case of supersonic aircraft, bulges and protrusions from the surface of the airframe can increase the strength of the sonic boom generated by the aircraft during supersonic flight. In another solution, rather than increasing the robustness of the various components of the above-described arrangement, additional linear actuators are employed instead. This is not desirable because it increases the cost, the weight, the part count, the number of failure points, and the overall complexity of the arrangement. Thus, while these solutions may be effective, there is room for improvement.
Accordingly, it is desirable to provide an aircraft and a control system arrangement that addresses the above described challenges. In addition, it is desirable to provide a method for assembling an aircraft that addresses the above described challenges. Furthermore, other desirable features and characteristics will become apparent from the subsequent summary and detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.